I've even tried the hard coded version above which is the commented line above. Any ideas guys?

EDIT:
I've tried using the url

domain.com/content.php?linkid=contact-us

which works correctly but

domain.com/contact-us

gives me the error The requested URL /contact-us was not found on this server..

I've also discovered another url that's not working and it is

domain.com/media/list/1

which says The requested URL /media.html/list/1 was not found on this server. I don't know where it's getting media.html from. There was a file named media.html in the file structure so I removed that and the link started working. That's not the case with contact-us though.

Translating above comments into an answer as it might help someone with similar problems.

You need to disable MultiViews options to make it work.

So just change your Options line this:

Options +FollowSymlinks -MultiViews

Option MultiViews is used by Apache's content negotiation module that runs beforemod_rewrite and makes Apache server match extensions of files. So if /file is the URL then Apache will serve /file.html.